\nThe C18 compiler does not support data buffers over 256 bytes without a modification to the linker script to define a larger bank of microcontroller ram.\n<\/p>\n
\nCopy the default linker script for your PIC18 device from:\n<\/p>\n
\nC:\\Program Files (x86)\\Microchip\\MPASM Suite\\LKR\n<\/p>\n
\ninto your projects directory. Add the file to your MPLAB project so that it is used in place of the default file.\n<\/p>\n
\nFind the section listing each of the databanks for your device, e.g.\n<\/p>\n
\r\n\r\nDATABANK NAME=gpr0 START=0x60 END=0xFF\r\nDATABANK NAME=gpr1 START=0x100 END=0x1FF\r\nDATABANK NAME=gpr2 START=0x200 END=0x2FF\r\nDATABANK NAME=gpr3 START=0x300 END=0x3FF\r\nDATABANK NAME=gpr4 START=0x400 END=0x4FF\r\nDATABANK NAME=gpr5 START=0x500 END=0x5FF\r\nDATABANK NAME=gpr6 START=0x600 END=0x6FF\r\nDATABANK NAME=gpr7 START=0x700 END=0x7FF\r\nDATABANK NAME=gpr8 START=0x800 END=0x8FF\r\nDATABANK NAME=gpr9 START=0x900 END=0x9FF\r\nDATABANK NAME=gpr10 START=0xA00 END=0xAFF\r\nDATABANK NAME=gpr11 START=0xB00 END=0xBFF\r\nDATABANK NAME=gpr12 START=0xC00 END=0xCFF\r\n#IFDEF _DEBUGDATASTART\r\n DATABANK NAME=gpr13 START=0xD00 END=_DATAEND\r\n DATABANK NAME=dbgspr START=_DEBUGDATASTART END=_DEND PROTECTED\r\n#ELSE \/\/no debug\r\n DATABANK NAME=gpr13 START=0xD00 END=0xDFF\r\n#FI\r\nDATABANK NAME=gpr14 START=0xE00 END=0xE40\r\n<\/code><\/pre>\n\nThe number will relate to the number of gpr banks your PIC18 device has.\n<\/p>\n
\nNow select as many consecutive databanks as you will need to be able to hold your array from somewhere in the middle of the available banks. If you need a multiple of 256bytes then you will use the complete banks, or otherwise you will use just part of the final bank. You want to delete those databanks (and just edit the START address for the final bank if not using a 256byte multiple) and then add your own new databank which will hold your array:\n<\/p>\n
\r\n\r\nDATABANK NAME=my_ram_section START=0x#00 END=0x#FF\r\n<\/code><\/pre>\n\nWhere ‘0x#00’ is the start address of the first removed bank and ‘0x#FF ‘ is the end address of the last removed bank. E.g. for a 512 byte databank in this example:\n<\/p>\n
\r\n\r\nDATABANK NAME=gpr0 START=0x60 END=0xFF\r\nDATABANK NAME=gpr1 START=0x100 END=0x1FF\r\nDATABANK NAME=gpr2 START=0x200 END=0x2FF\r\nDATABANK NAME=gpr3 START=0x300 END=0x3FF\r\nDATABANK NAME=gpr4 START=0x400 END=0x4FF\r\nDATABANK NAME=gpr5 START=0x500 END=0x5FF\r\nDATABANK NAME=gpr6 START=0x600 END=0x6FF\r\n\r\nDATABANK NAME=dmx_512_byte_ram_section START=0x700 END=0x8FF\r\n\r\nDATABANK NAME=gpr9 START=0x900 END=0x9FF\r\nDATABANK NAME=gpr10 START=0xA00 END=0xAFF\r\nDATABANK NAME=gpr11 START=0xB00 END=0xBFF\r\nDATABANK NAME=gpr12 START=0xC00 END=0xCFF\r\n#IFDEF _DEBUGDATASTART\r\n DATABANK NAME=gpr13 START=0xD00 END=_DATAEND\r\n DATABANK NAME=dbgspr START=_DEBUGDATASTART END=_DEND PROTECTED\r\n#ELSE \/\/no debug\r\n DATABANK NAME=gpr13 START=0xD00 END=0xDFF\r\n#FI\r\n<\/code><\/pre>\n\nSave the linker script. This defines the new block of memory and you can now use the name you assigned to declare your array:\n<\/p>\n
\r\n\r\n#pragma udata dmx_512_byte_ram_section\t\t\t\t\/\/This is the PIC C18 compiler command to use the specially defined section in the linker script (uses a modified linker script for this)\r\nBYTE dmx_tx_buffer[512];\t\t\t\/\/(C18 large array requirement to use a special big section of ram defined in the linker script)\r\n#pragma udata\r\n<\/code><\/pre>\n\nAccessing The Array
\n<\/h5>\n
\nIts OK to use pointers like this:\n<\/p>\n
\r\n\r\n\tBYTE *buffer_pointer;\r\n\tbuffer_pointer = &my_array[0] + some_value;\r\n\t*buffer_pointer = 0x01;\r\n<\/code><\/pre>\n\n <\/p>\n","protected":false},"excerpt":{"rendered":"
Creating Large Memory Arrays The C18 compiler does not support data buffers over 256 bytes without a modification to the linker script to define a larger bank of microcontroller ram. Copy the default linker script for your PIC18 device from: C:\\Program Files (x86)\\Microchip\\MPASM Suite\\LKR into your projects directory. Add the file to your MPLAB project so […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[52],"tags":[],"class_list":["post-362","post","type-post","status-publish","format-standard","hentry","category-memory-c18-compiler"],"_links":{"self":[{"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/posts\/362","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/comments?post=362"}],"version-history":[{"count":4,"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/posts\/362\/revisions"}],"predecessor-version":[{"id":417,"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/posts\/362\/revisions\/417"}],"wp:attachment":[{"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/media?parent=362"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/categories?post=362"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibex.tech\/embedded\/wp-json\/wp\/v2\/tags?post=362"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}